Figure 2: Expression of laterality genes is lost in sfw mutants.

(a–d) In situ hybridization analysis of lefty1 expression in wild-type (a,b) and sfw mutants (c,d). lefty1 is initiated in the caudal notochord in wild-type embryos at 12 hpf (5 somites; a, arrowhead) and its expression expands anteriorly in the midline over the course of somitogenesis (b, 16 hpf, 15 somites). In sfw mutants, lefty1 expression is initiated in the midline at 12 hpf (5 somites; c, arrowhead); however, it is not expressed in the midline at 16 hpf (d). (e,f) spaw expression starts around the KV (arrows) and is initiated in the LPM (arrowhead) of wild-type embryos at (14 hpf, 10 somites) (e) and propagates anteriorly during somitogenesis (16 hpf, 15 somites; f, arrowhead). In sfw mutants, spaw expression is initiated around the KV (arrows) and in the posterior LPM (arrowheads) at 14 hpf (g); however, spaw expression does not spread to anterior parts of the LPM later during somitogenesis (h). (i,j) cyclops is expressed in the left diencephalon (i) and left heart field (j) in wild-type embryos at 21 hpf (23 somites), but is absent from both domains in sfw mutant embryos (m,n). (k,l) Wild-type embryos express lefty2 in the left heart field (k) and pitx2 in the left LPM (l) at 22 hpf (25 somites); however, expression of both lefty2 in the heart and pitx2 in the left LPM is absent in sfw mutant embryos (o,p). Scale bars, 100 μM.